HUCKLEBERRY MOUNTAIN. 171 



the rhyolite of the summit the Montana beds present a very uneven surface, 

 and at one point the sandstones project through the capping- of lava, which 

 elsewhere forms the top of the mountain. On both the east and west slopes 

 of Huckleberry Mountain the underlying strata present many of the same 

 general features, being fissile, friable sandstone, crumbling- easily, and in 

 places showing signs of cross bedding and other evidences of shallow- water 

 deposition. On the west side, where the sandstones are exposed by erosion 

 of the rhyolite, the beds have yielded Cardium pauperculum, and on the east 

 side, just below the base of the rhyolite, the same species has been obtained 

 from nearly similar rock. Again, near the east end of the long spur 

 making out toward Coulter Creek, in fissile sandstone, inclined 10° S., 

 there were found the same Cardium, associated with Ostrea anomioides. 



North of Huckleberry Mountain the country suddenly falls away 

 several hundred feet to a narrow saddle, where the Montana shales are asrain 

 well shown. Beyond this saddle the country ag-ain rises in a prominent 

 point, which, for want of any distinctive appellation, may be designated as 

 North Huckleberry Mountain. In elevation it falls but little below the 

 more southern point, and commands to the north a still more comprehensive 

 view. Geologically the two points possess much in common. A sheet of 

 rhyolite, resting upon the Montana sandstone, forms the top of the table, as 

 already described for Huckleberry Mountain. Probably at one time the 

 two points were connected by a continuous sheet of rhyolite, erosion having- 

 since worn away the rock upon the saddle. In the case of North Huckle- 

 berry Mountain the rhyolite escarpment faces northward, and the prominent 

 wall of Montana sandstone stretches far away to the eastward till buried 

 beneath the outlying masses of late basic breccia. 



The fissile sandstones of the Montana beds are well shown all alono- the 

 northern slopes of the mountain and in the valley of the stream tributary 

 to Coulter Creek. Northward, the Montana sandstone still forms the 

 summit of the main ridge and eastern slopes, till, near the northern end of 

 the mountain, the beds become decidedly argillaceous, with sandstone occur- 

 ring as intercalated layers. Although no evidence of a fauna was obtained, 

 the beds, upon their lithological habit in distinction to the arenaceous beds 

 above, have been assigned to the Colorado formation. Their continuity 

 westward is obscured by overlying rhyolite. Montana sandstones occur as 

 the underlying rocks along the entire western slope of .this mountain mass, 



